A schottky barrier diode is a diode having rectification function utilizing an electron barrier formed in the interface of a metal and a semiconductor. As the semiconductor, Si is most commonly used (Patent Document 1, for example). Further, as a compound semiconductor having a band gap larger than that of Si, GaAs or, recently, SiC has been used (Patent Documents 2 and 3, for example).
A Si-based schottky diode is used in a high-speed switching element, a transmission/receiving mixer in a several GHz frequency band, or a frequency conversion device or the like. A GaAs-based schottky diode realizes a further higher-speed switching device, and is used in a converter, a mixer or the like for microwaves. Utilizing a wide band gap, SiC is expected to be used in an electric car, railroad, power transmission or the like in which a higher voltage is applied.
A schottky barrier diode is generally used due to its relatively low cost. However, since it has a small band gap of 1.1 eV, it is required to increase the size of the element in order to allow it to have a withstand voltage. The band gap of GaAs is 1.4 eV that is larger than that of Si and the withstand voltage of GaAs is superior to that of Si. However, epitaxial growth thereof on a Si substrate is difficult, and hence, it was difficult to obtain crystals suffering less dislocation. SiC has a wide band gap of 3.3 eV, and has a high dielectric breakdown field, and hence it is a material of which the performance is expected among other semiconductors. However, since both production of a substrate and epitaxial growth require high-temperature processes, use of SiC has problems in respect of mass productivity and cost.